For connecting a fuel injector to a fuel line, due to the installation situation, a connecting element may be necessary between the fuel injector and the fuel supply line for compensating the position tolerance. This is true, for example, in direct-injection internal combustion engines, which supply multiple fuel injectors with fuel via a shared fuel line, the fuel rail.
A fuel injection system having one adapter per injector is described in German Patent Application No. 197 35 665. The adapter described there has two different connections. On one side, the adapter has a connecting sleeve which may be inserted into an opening of the fuel line. On the opposite end, a receiver opening is introduced into the adapter, into which the connection side of the fuel injector may be inserted. In this case, the receiver opening has, for example, an internal geometry which is identical to the opening in the fuel line. The adapter thus acts like an extension of the fuel injector or of the connecting sleeve of the fuel line. A peripheral shoulder is made on the outside of the adapter, via which the adapter may be connected to the fuel line by a holding clamp and secured against slipping out.
The adapter is sealed by two sealing elements, which may be formed as O-rings. The first sealing element, which is used to seal the adapter in relation to the fuel line, is positioned in a groove on the connecting sleeve of the adapter in this case. In contrast, the seal between the fuel injector and the adapter is produced by a second sealing element positioned on the fuel injector.
Using the adapter described in German Patent Application No. 197 35 665, it may be necessary to fix the adapter on the fuel rail using a holding clamp. This requires not only an additional work step during the assembly of the internal combustion engine, but also additional expenditure for parts. In addition, the spacer may need to be inserted with a certain orientation during assembly.
Furthermore, the limited elasticity of the holding clamp results in the adapter having force applied to it unequally in the event of tilting of the adapter in relation to the fuel line, so that pinching of the sealing element and, finally, failure of the sealing element, may occur.
An additional clamping shoe may be necessary to fix the fuel injector in the cylinder head of the internal combustion engine. The adapter is unable to transmit axial forces and, due to its restricted movability, is only able to compensate position tolerances to a limited degree. For example, in long fuel rails, temperature variations which may occur during operation of an internal combustion engine result in relatively large changes in length of the fuel line and, for example, in long fuel rails, to changes in length of the connecting sleeves which cannot be compensated for.